Multi-start closures for open implants

ABSTRACT

An open implant closure structure includes a helically wound guide and advancement structure having at least two helically wound forms thereon providing a multi-start closing mechanism for use between spaced arms of a cooperating open medical implant having mating helically wound structure thereon. Illustrated structures include interlocking flange forms, v-threads, square threads, reverse angle threads and buttress threads and receivers with break-off extensions and cooperating tooling.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 61/631,746 filed Jan. 10, 2012, that isincorporated by reference herein. This application also claims thebenefit of U.S. Provisional Patent Application Ser. No. 61/634,361 filedFeb. 28, 2012, that is incorporated by reference herein.

BACKGROUND OF THE INVENTION

The present invention is directed to structure for joining togetherparts of a medical implant, in particular to closure mechanisms for usewith open bone anchors in spinal surgery, and in some embodimentsthereof, for use with spinal bone anchors such as polyaxial screws.

Bone anchors, such as bone screws and hooks are utilized in many typesof spinal surgery in order to secure various implants to vertebrae alongthe spinal column for the purpose of stabilizing and/or adjusting spinalalignment. For example, the most common mechanism for providingvertebral support is to implant bone screws into certain bones whichthen in turn support a rod or are supported by the rod. Although bothclosed-ended and open-ended bone anchors are known, open-ended anchorsare particularly well suited for connections to longitudinal connectingmembers such as hard, soft or deformable rods, dynamic or elasticconnectors and connector arms, because such rods or other connectormembers do not need to be passed through a closed bore, but rather canbe laid or urged into an open channel within a receiver or head of sucha bone anchor. Generally, the anchors must be inserted into the bone asan integral unit or a preassembled unit, in the form of a shank or hookand connected pivotal receiver. In some instances, a portion of such apreassembled unit, such as a shank of a polyaxial bone screw assembly,may be independently implanted into bone, followed by push- or pop-onassembly of a receiver portion of the unit.

Typical open-ended bone screws include a threaded shank with a head orreceiver having a pair of parallel projecting branches or arms whichform a yoke with a U-shaped slot or channel to receive a rod or otherlongitudinal connecting member. Hooks and other types of connectors, asare used in spinal fixation techniques, may also include similar openends for receiving rods or portions of other fixation and stabilizationstructure. The open-ended head or rod receiver portion of such implantstypically includes a pair of spaced arms forming a channel closed by aclosure member after the rod or other longitudinal connecting member isplaced in the channel. Known closures include slide-on types, twist-onvarieties that are rotated ninety degrees to a locked in position, and avariety of single start helically wound guide and advancement structuresincluding, for example, thread forms having v-thread, reverse-anglebuttress or square thread forms, to name a few, as well as othernon-threadlike helically wound forms. Sometimes threaded plugs areutilized with outer threaded nuts to prevent splaying of the receiverarms.

As indicated above, the force required to press a closure structure downonto a rod or other connector located between arms of an open implant isconsiderable. Even though a head or receiver portion of an openpolyaxial bone anchor may be pivoted in a direction to make it easierfor the arms of the open implant to receive a rod or other connector,spinal misalignments, irregularities and the placement of other surgicaltools make it difficult to place the rod or other connector between thearms of the implant while a closure structure is mated with the openimplant as well as used to push the rod or other connector downwardlyinto the implant. For example, when the closure is a cylindrical plughaving a single start helically wound guide and advancement structure,such structure must be aligned with mating structure on one of theimplant arms and then rotated until a portion of the structure iscaptured by mating guide and advancement structure on both arms of theimplant, all the while the closure is being pressed down on the rodwhile other forces are pushing and pulling the rod back out of theimplant. Integral or mono-axial open implants that cannot be pivoted toreceive the rod are even more difficult to manipulate during the initialplacement of the rod and initial mating rotation of a closure plugbetween the spaced, open arms of the implant. Therefore, extraordinaryforces are placed on the implant and closure plug while the surgeoneither pushes down on the rod or pulls up on the bone to get the rod inposition between the implant arms and to initially push down upon therod with the closure plug.

SUMMARY OF THE INVENTION

A closure structure, top or plug of the invention for insertion betweenspaced arms of an open medical implant includes one or more helicallywound guide and advancement features, each feature having a startsurface or structure located at or near a bottom surface of the closureplug, each start structure simultaneously engaging and being captured byeach of the spaced arms of the open implant upon initial rotation of theclosure structure with respect to the open implant arms. According to anaspect of the invention, a double-start closure is disclosed having twohelically wound forms thereon, each form having a start structure forsimultaneously engaging a mating helical form on a respective openimplant arm. Each time the illustrated duel- or double-start closureplug is rotated one turn (three hundred sixty degrees) between theimplant arms, the closure plug advances axially into the implant andtoward the rod by a width of two helical forms. The helically woundforms of the multi-start closure spiral around a cylindrical plug bodythereof to an extent that the closure rotates over ninety degrees tofully or substantially receive the entire closure plug between the armsof the open implant. The illustrated closure is sized for at least onecomplete rotation (three hundred sixty degrees) of the plug with respectto the open implant to substantially receive the plug between theimplant arms. Multi-start closures of the invention may have two or morecoarse or fine helical forms, resulting in fewer or greater forms peraxial distance spiraling about the closure plug body and thus resultingin plugs that rotate less (when more coarse) or more (when thin or fine)than one complete rotation to be fully received between the implantarms, typically, at least a ninety-one degree rotation is preferred.

An illustrated multi-start closure and mating open implant is in theform of non-threaded, interlocking flange forms. Also disclosed aremulti-start closure structures provided with helically wound forms ofother geometry, including, but not limited to helically wound threadssuch as reverse angle, buttress, square and v-threads. The multi-startclosure may be cannulated for minimally invasive surgical applications.

Another illustrated multi-start closure embodiment of the invention isshown with a bone screw assembly having an open receiver with a pair ofopposed arms, each arm having guide and advancement structure forsimultaneous mating engagement with a start of the helically woundmulti-start closure. A further embodiment according to the inventionincludes an open bone anchor receiver having integral upwardly extendingbreak-off tabs that also have the guide and advancement structure formating with the multi-start closure. A further embodiment includes anattachable/detachable guide tool cooperating with such a multi-startopen receiver, the tool having inner guide and advancement structureslocated near a bottom thereof for rotatably and matingly receiving themulti-start closure and being synchronized with the receiver guide andadvancement structure for rotating and driving the multi-start closuredownward from the guide tool to the receiver.

Objects of the invention further include providing apparatus and methodsthat are easy to use and especially adapted for the intended use thereofand wherein the tools are comparatively inexpensive to produce. Otherobjects and advantages of this invention will become apparent from thefollowing description taken in conjunction with the accompanyingdrawings wherein are set forth, by way of illustration and example,certain embodiments of this invention.

The drawings constitute a part of this specification and includeexemplary embodiments of the present invention and illustrate variousobjects and features thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an embodiment of a multi-start closureaccording to the invention.

FIG. 2 is another perspective view of the multi-start closure of FIG. 1.

FIG. 3 is a front elevational view of the closure of FIG. 1 shown with aportion of a receiver of a polyaxial bone screw according to FIG. 8, thereceiver shown in partial front elevation with portions broken away toshow the detail thereof, and further showing a rod being pressed upon bythe closure, the rod also in partial front elevation with portionsbroken away to show the detail thereof.

FIG. 4 is a reduced top plan view of the closure of FIG. 1.

FIG. 5 is a reduced bottom plan view of the closure of FIG. 1.

FIG. 6 is an enlarged front elevational view of the closure of FIG. 1with portions broken away to show the detail thereof.

FIG. 7 is a reduced cross-sectional view taken along the line 7-7 ofFIG. 6.

FIG. 8 a partial front elevational view of an open bone screw assembly,with portions broken away to show the detail thereof, including areceiver, a shank, a compression insert and also shown in engagementwith the closure top of FIG. 1 (in reduced view) and a longitudinalconnecting member in the form of a hard rod.

FIG. 9 is a front elevational view of an alternative closure of anembodiment of the invention, similar to the closure of FIG. 1, butincluding a break-off head, the alternative closure shown with a portionof a receiver of the polyaxial bone screw of FIG. 8 shown in enlargedand partial front elevation with portions broken away to show the detailthereof, and further showing a rod being pressed upon by the alternativeclosure, the rod also in partial front elevation with portions brokenaway to show the detail thereof.

FIG. 10 is another front elevational view of the closure of FIG. 9 withportions broken away to show the detail thereof.

FIG. 11 is a front elevational view of an alternative square-threadclosure of an embodiment of the invention with portions broken away toshow the detail thereof, the closure shown with a portion of a receiverof the polyaxial bone screw of FIG. 8 shown in enlarged and partialfront elevation with portions broken away to show the detail thereof,and further showing a rod being pressed upon by the alternative closure,the rod also in partial front elevation with portions broken away toshow the detail thereof.

FIG. 12 is a front elevational view of an alternative reverse angleclosure of an embodiment of the invention with portions broken away toshow the detail thereof, the closure shown with a portion of a receiverof the polyaxial bone screw of FIG. 8 shown in enlarged and partialfront elevation with portions broken away to show the detail thereof,and further showing a rod being pressed upon by the alternative closure,the rod also in partial front elevation with portions broken away toshow the detail thereof.

FIG. 13 is a front elevational view of an alternative v-thread closureembodiment of the invention with portions broken away to show the detailthereof, the closure shown with a portion of a receiver of the polyaxialbone screw of FIG. 8 shown in enlarged and partial front elevation withportions broken away to show the detail thereof, and further showing arod being pressed upon by the alternative closure, the rod also inpartial front elevation with portions broken away to show the detailthereof.

FIG. 14 is a front elevational view of an alternative buttress-threadclosure embodiment of the invention with portions broken away to showthe detail thereof, the closure shown with a portion of a receiver ofthe polyaxial bone screw of FIG. 8 shown in enlarged and partial frontelevation with portions broken away to show the detail thereof, andfurther showing a rod being pressed upon by the alternative closure, therod also in partial front elevation with portions broken away to showthe detail thereof.

FIG. 15 is a partial front elevational view of an embodiment of amulti-start open bone anchor receiver of an embodiment of the inventionwith portions broken away to show the detail thereof, the receiverincluding break-off tabs.

FIG. 16 is an enlarged and partial front elevational view of thereceiver of FIG. 15 with portions broken away to show the detailthereof.

FIG. 17 is a partial front elevational view of an embodiment of a boneanchor receiver having a guide and advancement structure that matinglycooperates with the multi-start closure of FIG. 1, also shown in frontelevation, the receiver having portions broken away to show the detailthereof, and further shown with a guide tool, shown in phantom, theguide tool having a multi-start guide and advancement structurereceiving inner surface synchronized with the bone anchor receiver guideand advancement structure.

DETAILED DESCRIPTION OF THE INVENTION

As required, detailed embodiments of the present invention are disclosedherein; however, it is to be understood that the disclosed embodimentsare merely exemplary of the invention, which may be embodied in variousforms. Therefore, specific structural and functional details disclosedherein are not to be interpreted as limiting, but merely as a basis forthe claims and as a representative basis for teaching one skilled in theart to variously employ the present invention in virtually anyappropriately detailed structure. It is also noted that any reference tothe words top, bottom, up and down, and the like, in this applicationrefers to the alignment shown in the various drawings, as well as thenormal connotations applied to such devices, and is not intended torestrict positioning of the bone attachment structures in actual use.

Furthermore, the terms lead, pitch and start, as such terms are used todescribe helically wound guide and advancement structures, are to beunderstood as follows: Lead is a distance along the axis of a closureplug that is covered by one complete rotation (360 degrees) of theclosure plug with respect to a mating open implant. Pitch is thedistance from a crest (or outer point or location) of one guide andadvancement structure form to the next. For example in a single-startthread-form, such as a single start, helically wound v-thread closureplug, lead and pitch are the same. Single start means that there is onlyone ridge or helically wound form wrapped around a cylindrical core, orin the case of the present invention, wrapped around a cylindricalclosure plug body and thus there is only one start structure or surfaceat a base or forward end of the closure body that initially engages amating structure on the open implant. Each time a single start closurerotates one turn (360 degrees), the closure has advanced axially by awidth of one ridge or one helical form. Double-start means that thereare two ridges or forms wrapped around a core body and thus there aretwo starting surfaces or structures on the closure plug. Therefore, eachtime a double-start body rotates one turn (360 degrees), such a body hasadvanced axially by a width of two ridges or forms. Multi-start meansthat there are at least two and may be up to three or more of suchridges or forms wrapped around a core body.

With reference to FIGS. 1-8, and in particular to FIG. 8, the referencenumber 1 generally represents an open implant in the form of a polyaxialbone screw apparatus or assembly that cooperates with an illustratedclosure structure 18 embodiment of the invention. The bone screwassembly 1 is described in detail in U.S. Provisional Patent ApplicationNo. 61/631,746 filed Jan. 10, 2012 and incorporated by reference herein(hereafter the '746 application) and therefore will not be described ingreat detail herein. The description set forth in the '746 applicationincludes a more detailed explanation of all the components referenced inFIG. 8. It is noted that multi-start closure embodiments of theinvention, such as the closure 18 may be used with a variety of openimplants including, but not limited to a wide variety of polyaxialscrews, mono-axial or fixed screws, hooks and other types of openimplants requiring a plug or closure mechanism to fix a rod or otherimplant member to a vertebra or other bone. Thus, the assembly 1 is onlyone example of how multi-start closures of the invention may be used.

Briefly, the illustrated assembly 1 includes a shank 4 with an upwardlyextending upper portion or capture structure 8; an open receiver 10; aretaining structure or retainer (not shown) that pivots with the shank4, a compression or pressure insert 14 and the multi-start closurestructure or plug 18 in the form of a cylindrical plug having adouble-start helically wound flange-form. The closure structure 18presses against and captures a longitudinal connecting member, forexample, a rod 21 which in turn engages the compression insert 14 thatpresses against the shank upper portion 8 that is attached to theretaining structure that in turn presses against an inner surface of thereceiver 10, so as to capture and fix the longitudinal connecting member21 within the receiver 10 and thus fix the member 21 relative to avertebra (not shown). The illustrated receiver 10 and the shank 4cooperate in such a manner that the receiver 10 and the shank 4 can besecured at any of a plurality of angles, articulations or rotationalalignments relative to one another and within a selected range of anglesboth from side to side and from front to rear, to enable flexible orarticulated engagement of the receiver 10 with the shank 4 until bothare locked or fixed relative to each other near the end of animplantation procedure.

The illustrated rod 21 is hard, stiff, non-elastic and cylindrical,having an outer cylindrical surface 22. However, in other embodiments,the rod 21 may be elastic, deformable and/or of a differentcross-sectional geometry. The rod 21 may be made from a variety ofmetals, metal alloys and deformable and less compressible plastics,including, but not limited to rods made of elastomeric,polyetheretherketone (PEEK) and other types of materials, such aspolycarbonate urethanes (PCU) and polyethylenes. Furthermore, in lieu ofa rod, longitudinal connecting members for use with the assembly 1 maytake a variety of shapes, and/or may include a tensioned cord asdescribed in greater detail in the '746 application that is incorporatedby reference herein.

It is noted that the receiver 10 includes guide and advancementstructures 168 that are shown as interlocking flange forms described ingreater detail in applicant's U.S. Pat. No. 6,726,689, also incorporatedby reference herein. Alternately, when the closure structure includes adifferent helical form, the receiver cooperating structures (e.g., 168)must also be of a cooperating, mating geometry, such as a square-shapedthread receiving form, a buttress thread receiving form, a reverse anglethread receiving form or other thread-like or non-thread-like helicallywound discontinuous advancement structure receiving forms for operablyguiding under rotation and advancing a multi-start closure structuredownward between the receiver arms 160, as well as eventual torquingwhen the closure structure abuts against the rod 21 or other connectingmember.

With particular reference to FIGS. 1-7, the illustrated multi-startclosure structure 18 is a double start closure having a substantiallycylindrical plug body 40 having an axis of rotation that is the same asthat of the receiver 10 and including a helically wound guide andadvancement structure in the form of a pair of helically wound forms 42and 43, each illustrated as an interlocking flange form that operablyjoins with mating flange form guide and advancement structures 168disposed on the arms of the receiver 10. The form 42 includes a startsurface or structure 46 and the form 43 includes a start surface orstructure 47. Each helically wound form 42 and 43 may take a variety offorms and geometries, including those described in Applicant's U.S. Pat.No. 6,726,689, which is incorporated by reference herein. It is noted(and also described in greater detail subsequently herein) that each ofthe closure structure guide and advancement structures or forms 42 and43 could alternatively be in the form of a buttress thread, a squarethread, a reverse angle thread, a v-thread or other thread like ornon-thread like helically wound advancement structures, for operablyguiding under rotation and advancing the closure structure downwardbetween the arms of the receive 10 and preferably having such a natureas to resist splaying of the receiver arms when the closure structure 18is advanced into the receiver channel. The specific flange forms 42 and43 illustrated in FIGS. 1-7, as well as acceptable alternative lockingforms, are described in detail in Applicant's U.S. Pat. No. 6,726,689,incorporated by reference herein, and thus shall not be discussedfurther herein. Such interlocking flange forms are preferred as theadded strength provided thereby beneficially cooperate with and counterany reduction in strength caused by the any reduced profile of thereceiver 10 that may more advantageously engage longitudinal connectingmember components.

The illustrated closure structure 18 also includes a top surface 54 withan internal drive 56 in the form of an aperture that is illustrated as astar-shaped internal drive such as that sold under the trademark TORX,or may be, for example, a hex drive, or other internal drives such asslotted, tri-wing, spanner, two or more apertures of various shapes, andthe like. A driving tool (not shown) sized and shaped for engagementwith the internal drive 56 is used for both rotatable engagement and, ifneeded, disengagement of the closure 18 from the receiver 10 at arms160. A base or bottom surface 58 of the closure is planar and furtherincludes a rim 60 for engagement and penetration into the surface 22 ofthe rod 21 in certain embodiments of the invention. The closure top 18further includes a cannulation through bore 62 extending along a centralaxis thereof and through a drive base surface 63 and the bottom surface58 thereof. Such a through bore provides a passage through the closure18 interior for a length of wire (not shown) inserted therein to providea guide for insertion of the closure top into the receiver arms 160.

The closure structure 18 helically wound flange form start structures 46and 47 of the respective forms 42 and 43 are located on opposite sidesof the closure plug body 40 and are both located adjacent the bottomsurface 58. As illustrated in FIG. 3, for example, when the closurestructure 18 is rotated into the receiver 10 between receiver arms 160,each having a guide and advancement structure 168, the start 46 engagesmating guide and advancement structure 168 on one arm 160 and the start47 simultaneously engages guide and advancement structure 168 on theopposing arm 160, both forms 42 and 43 being simultaneously captured bythe mating forms 168 on the opposed arms 160. As the structure 18 isrotated, the structure advances axially downwardly between the arms 160and presses evenly down upon the captured rod 21. Each time theillustrated duel- or double-start closure plug 18 is rotated onecomplete turn or pass (three hundred sixty degrees) between the implantarms, the closure plug 18 advances axially into the implant and towardthe rod by a width of two helical flange forms. The illustrated closure18 is sized for at least one complete rotation (three hundred sixtydegree) of the plug 18 with respect to the receiver 10 open arms 160 tosubstantially receive the plug between the implant arms. Multi-startclosures of the invention may have two or more coarse or fine helicalforms, resulting in fewer or greater forms per axial distance spiralingabout the closure plug body and thus resulting in plugs that rotate lessor more than one complete rotation to be fully received between theimplant arms. Preferably, helically wound forms of the multi-startclosure of the invention are sized so as to spiral around a cylindricalplug body thereof to an extent that the closure rotates at leastninety-one degrees to fully or substantially receive the closure plugbetween the arms of the bone screw receiver or other open implant.Particularly preferred guide and advancement structures are sized for atleast one complete turn or pass (three-hundred sixty degree) of theclosure between the receiver 10 arms and as many as two to threerotations to be fully received between implant arms.

In use, the receiver 10, the retainer 12 and the compression insert 14are assembled with the shank 4 either before or after the shank isimplanted into a vertebra, and the resulting assembly 1 is ultimatelyattached to the rod 21 or other longitudinal connecting member asdescribed in the '746 application incorporated by reference herein. Itis noted that the shank 4 and other bone screw assembly parts, the rod21 (also having a central lumen in some embodiments) and the closure top18 having the central bore 62 can be inserted in a percutaneous orminimally invasive surgical manner, utilizing guide wires. After the rod21 or other longitudinal connecting member is positioned in an open orpercutaneous manner in cooperation with the at least two bone screwassemblies 1 (or other open implants), the closure structure 18 is theninserted into and advanced between the arms 160 of each of the receiver10. The closure structure 18 is rotated, using a tool engaged with theinner drive 56 until a selected pressure is reached at which point therod 21 engages a U-shaped seating surface of the compression insert 14,further pressing the insert against the shank upper portion 8 andattached retainer into locked frictional engagement with the receiver10. Prior to locking the insert 14 against the shank head 8, the shank 4may be pivoted to a plurality of potentially desirable positions withrespect to the receiver 10, followed by locking of the polyaxialmechanism by fully mating the multi-start closure top 18 with thereceiver 10. Different angular or articulated positions of the shank 4with respect to the receiver 10 are shown in the '746 applicationincorporated by reference herein.

With specific reference to FIGS. 3 and 8, as the multi-start closurestructure 18 rotates and moves downwardly into the respective receiver10, the rim 60 engages and penetrates the rod surface 22, the closurestructure 18 pressing downwardly against and biasing the rod 21 intocompressive engagement with the insert 14 that urges the shank upperportion 8 and attached retainer into locking engagement with thereceiver, the retainer outer surface frictionally abutting an innerspherical seating surface of the receiver 10. For example, about 80 toabout 120 inch pounds of torque on the closure top may be applied forfixing the bone screw shank 6 with respect to the receiver 10. Also, forexample, when the shank 4 is disposed at an angle with respect to thereceiver 10, a part of the shank upper portion 8 may also be infrictional engagement with a portion of the receiver spherical seatingsurface.

If removal of the rod 21 from any of the bone screw assemblies 1 isnecessary, or if it is desired to release the rod 21 at a particularlocation, disassembly is accomplished by using the driving tool (notshown) that mates with the internal drive 56 on the closure structure 18to rotate and remove such closure structure from the cooperatingreceiver 10. Disassembly is then accomplished in reverse order to theprocedure described previously herein for assembly.

With reference to FIGS. 9 and 10, an alternative closure top 18′ isshown that is almost identical to the closure top 18. However, the top18′ differs from the top 18 in that the top 18′ includes a break-offhead 70′ that further includes a top surface 72′ having tooling notches73′, an outer faceted driving surface 74′, illustrated as having ahex-shaped profile, and an inner bore 76′. Otherwise, the closure top18′ includes a body 40′, a first helical form 42′, a second helical form43′, a body top surface 54′, a body internal drive 56′, a base 58′, arim 60′, a cannulation bore 62′ and a drive base surface 63′ that is thesame or substantially similar to the respective body 40, first helicalform 42, second helical form 43, body top surface 54, internal drive 56,base 58, rim 60, cannulation bore 62 and drive base surface 63previously described herein with respect to the closure top 18. Thebreak-off head 70′ is integral with the body 40′ at the body top surface54′. The inner bore 76′ communicates with the inner drive 56′ and thecannulation bore 62′. The break-off head 70′ is designed to allow suchhead 70′ to break from the body 40′ at or near the top surface 54′ at apreselected torque, for example, 70 to 140 inch pounds, when ahex-shaped tool (not shown) engages the outer surfaces 74′ and drivesthe closure structure 18′ into the receiver 10 as shown in FIG. 9. Theinner drive 56′ is used for disassembly or loosening of the closure 18′from the receiver 10, and re-tightening, if needed.

With reference to FIG. 11, another alternative multi-start closure top318 is shown that is almost identical to the closure top 18 with theexception that the two flange forms 42 and 43 with respective starts 46and 47 have been replaced with square threads 342 and 343 withrespective starts 346 (not shown) and 347. Otherwise, the dual or doublestart closure top 318 includes a body 340, a body top surface 354, abody internal drive 356, a base 358, a rim 360′, a cannulation bore 362and a drive base surface 363 that is the same or substantially similarto the respective body 40, body top surface 54, internal drive 56, base58, rim 60, cannulation bore 62 and drive base surface 63 previouslydescribed herein with respect to the closure top 18. In FIG. 11, theclosure top 318 is shown partially wound into a polyaxial bone screwreceiver 310 having opposed arms 360 with inner surfaces equipped withguide and advancement structures 368 that are sized and shaped tosimultaneously closely receive and mate with the square threads 342 and343 of the double closure structure 318. Otherwise, the receiver 310 isidentical or substantially similar to the receiver 10 described indetail in the '746 application incorporated by reference herein.

With reference to FIG. 12, an alternative multi-start closure top 418 isshown that is almost identical to the closure top 18 with the exceptionthat the two flange forms 42 and 43 with respective starts 46 and 47have been replaced with reverse angle threads 442 and 443 withrespective starts 446 (not shown) and 447. Otherwise, the dual or doublestart closure top 418 includes a body 440, a body top surface 454, abody internal drive 456, a base 458, a rim 460′, a cannulation bore 462and a drive base surface 463 that is the same or substantially similarto the respective body 40, body top surface 54, internal drive 56, base58, rim 60, cannulation bore 62 and drive base surface 63 previouslydescribed herein with respect to the closure top 18. The closure top 418is shown partially wound into a polyaxial bone screw receiver 410 havingopposed arms 460 with inner surfaces equipped with guide and advancementstructures 468 that are sized and shaped to simultaneously closelyreceive and mate with the reverse angle threads 442 and 443 of thedouble start closure structure 418. Otherwise, the receiver 410 isidentical or substantially similar to the receiver 10 described indetail in the '746 application incorporated by reference herein.

With reference to FIG. 13, another alternative multi-start closure top518 is shown that is almost identical to the closure top 18 with theexception that the two flange forms 42 and 43 with respective starts 46and 47 have been replaced with v-threads 542 and 543 with respectivestarts 546 (not shown) and 547. Otherwise, the dual or double startclosure top 518 includes a body 540, a body top surface 554, a bodyinternal drive 556, a base 558, a rim 560′, a cannulation bore 562 and adrive base surface 563 that is the same or substantially similar to therespective body 40, body top surface 54, internal drive 56, base 58, rim60, cannulation bore 62 and drive base surface 63 previously describedherein with respect to the closure top 18. The closure top 518 is shownpartially wound into a polyaxial bone screw receiver 510 having opposedarms 560 with inner surfaces equipped with guide and advancementstructures 568 that are sized and shaped to simultaneously closelyreceive and mate with the threads 542 and 543 of the double startclosure structure 518. Otherwise, the receiver 510 is identical orsubstantially similar to the receiver 10 described in detail in the '746application incorporated by reference herein.

With reference to FIG. 14, another alternative multi-start closure top618 is shown that is almost identical to the closure top 18 with theexception that the two flange forms 42 and 43 with respective starts 46and 47 have been replaced with buttress threads 642 and 643 withrespective starts 446 and 447 (not shown). Otherwise, the dual or doublestart closure top 618 includes a body 640, a body top surface 654, abody internal drive 656, a base 658, a rim 660′, a cannulation bore 662and a drive base surface 663 that is the same or substantially similarto the respective body 40, body top surface 54, internal drive 56, base58, rim 60, cannulation bore 62 and drive base surface 63 previouslydescribed herein with respect to the closure top 18. The closure top 618is shown partially wound into a polyaxial bone screw receiver 610 havingopposed arms 660 with inner surfaces equipped with guide and advancementstructures 668 that are sized and shaped to simultaneously closelyreceive and mate with the buttress threads 642 and 643 of the doublestart closure structure 618. Otherwise, the receiver 610 is identical orsubstantially similar to the receiver 10 described in detail in the '746application incorporated by reference herein.

With reference to FIGS. 15 and 16, an open receiver 710 is illustratedthat is substantially similar to the receiver 10 previously describedherein with the exception that the receiver 710 includes opposed arms760, each having an integral upstanding break-off extension 761. Eachreceiver arm 760 and integral extension 761 has an inner helically woundguide and advancement structure 768 that is sized and shaped to matewith the flange forms 42 and 43 of the dual start closure 18 previouslydescribed herein. The break-off extensions 761 are initially integralwith the respective arms 760 and are then broken off by a user after theclosure 18 has been rotatingly advanced along the arm extensions 761 andinto the channel located between the receiver arms 760. In theillustrated embodiment, in addition to an outer groove or notch 770located at or near a top surface 769 of each of the arms 760 where theextensions 761 break off from the receiver arms, illustrated inner armsurfaces include a recess or cut 771, best shown in FIG. 16, that runssubstantially horizontally. Each recess 771 is curved and elongate anddisposed somewhat cross-wise or transverse to the respective flange form768. For example, with reference to the arm 760 shown in FIG. 16, therecess 771 cuts into a weakened region, generally. 780, where the arm760 joins with the respective attached adjacent extension 761, thecurved and elongate recess 771 beginning at a lower portion or location781 of the flange form recess or segment and terminating at an opposedupper end location of the flange form segment, while otherwise leavingthe flange form 768 intact. Stated in another way, the substantiallyhorizontally extending recess 771 cuts into both a lead portion and atrailing portion of each of the flange form segments located near anddirectly above the opposed arms 760 and substantially opposite the notch770, thus further weakening the region where the extension and the armattach, without destroying the flange form path, so that the closure 18is not derailed by the recess 771 or otherwise prohibited from movingdownwardly into the receiver channel formed between the receiver arms760.

With reference to FIG. 17, the multi-start closure 18 is showncooperating with a spinal implant receiver, such as a bone screwreceiver 10′ and a discrete, detachable guide tool 801. The elongateguide tool 801, only partially shown in FIG. 17, is typically sized forextending from the bone screw receiver 10′ upwardly to a locationoutside of a patient, the tool providing a guide channel for operablyguiding the rod 21 or other longitudinal connecting member from aposition exterior of the bone screw receiver 10′ toward and into thebone screw receiver 10′. The illustrated guide tool has opposed arms805, each arm having a helical guide and advancement structure 810thereon that is illustrated as a square thread form, but may be of othergeometry, including a flange form the same or similar to the flangeforms 168′ of the receiver 10′ that mates with the flange forms 42 and43 of the closure structure 18. Thus, the illustrated structures 810 aresized and shaped for receiving and rotating engagement with a dual startclosure. The closure 18 is shown partially wound into the receiver 10′that is identical or substantially similar to the receiver 10 with theexception of certain outer arm surface features (not shown). Thus, thereceiver 10′ includes opposed arms 160′ with inner surfaces having guideand advancement structures 168′ that are sized and shaped tosimultaneously closely receive and mate with the flange forms 42 and 43of the dual start closure structure 18. The guide tool 801 includesattachment structure for detachable attachment to the receiver 10′(notshown), that may take a variety of forms and methods, including, but notlimited to a slide-on, slide-off attachment, a snap-on, rotate offattachment, a rotate-on and rotate-off attachment, to name a few. Forexample, cooperating attachment structure for both the tool and thereceiver may be used that is disclosed in U.S. Pat. No. 7,470,279 andincorporated by reference herein. Returning to the inner helically woundguide and advancement structure 810 formed on each arm 804 of the guidetool 801, the structure 810 is sized and shaped for being aligned withthe receiver arms 160′ during removable attachment of the tool 801 withthe respective bone screw receiver 10′ so as to continue the helicalpathway for the closure 18, the structures 810 being synchronized withthe flange forms 168′ to allow for the rotation and driving transfer ofthe closure 18 from the tool 801 into the receiver 10′.

It is to be understood that while certain forms of the present inventionhave been illustrated and described herein, it is not to be limited tothe specific forms or arrangement of parts described and shown.

The invention claimed is:
 1. In a medical implant having a substantially cylindrical closure member and a receiver member having first and second spaced arms forming an open channel, the closure member having an axis of rotation for closing the open channel, the improvement comprising: a) first and second helically wound forms located on the closure member, the first form having a first start and the second form having a second start; and b) a first discontinuous helically wound structure on the receiver first arm and a second discontinuous helically wound structure on the receiver second arm and wherein simultaneous mating of the first start with the arm first helically wound structure and the second start with the arm second helically wound structure occurs when the closure member is rotated between the first and second arms of the receiver member.
 2. The improvement of claim 1 wherein the first and second helically wound forms are each a flange form that interlocks with the respective helically wound structures on the receiver.
 3. The improvement of claim 1 wherein the first and second helically wound forms are v-threads.
 4. The improvement of claim 1 wherein the first and second helically wound forms are square threads.
 5. The improvement of claim 1 wherein the first and second helically wound forms are reverse angle threads.
 6. The improvement of claim 1 wherein the first and second helically wound forms are buttress threads.
 7. The improvement of claim 1 wherein the closure member has a break-off head.
 8. The improvement of claim 1 wherein the receiver has break-off extensions.
 9. The improvement of claim 1 further comprising a guide tool having third and fourth arms detachably attached to the receiver, the guide tool having a third discontinuous helically wound structure on the guide tool third arm and a fourth discontinuous helically wound structure on the guide tool fourth arm and wherein simultaneous mating of the first start with the third helically wound structure and the second start with the fourth helically wound structure occurs when the closure member is rotated between the third and fourth arms of the guide tool, the guide tool third and fourth helically wound structures sized and shaped to provide transfer of the closure member between the guide tool and the bone screw upon rotation of the closure.
 10. A medical implant comprising: a) a receiver having a body and a pair of upstanding spaced arms forming a channel for receiving a longitudinal connecting member, each arm having an inwardly facing surface with a first discontinuous helically wound guide and advancement structure located thereon; and b) a closure structure having a cylindrical body and a second helically wound guide and advancement structure having at least two starts.
 11. The implant of claim 10 wherein the first and second helically wound guide and advancement structures are interlocking flange forms.
 12. The improvement of claim 10 wherein the second helically wound guide and advancement structure includes at least two v-threads.
 13. The improvement of claim 10 wherein the second helically wound guide and advancement structure includes at least two square threads.
 14. The improvement of claim 10 wherein the second helically wound guide and advancement structure includes at least two reverse angle threads.
 15. The improvement of claim 10 wherein the second helically wound guide and advancement structure includes at least two buttress threads.
 16. The improvement of claim 10 wherein the closure structure has a break-off head.
 17. The improvement of claim 10, wherein the receiver has break-off extensions.
 18. In a medical implant, the improvement comprising: a) an open receiver member with spaced arms having inwardly facing surfaces, each with a helically wound guide and advancement form located thereon; and b) a helically wound multi-start closure member having an axis of rotation, the closure member rotatably mounted on the receiver member at the spaced arm inwardly facing surfaces.
 19. The improvement of claim 18 wherein the multi-start closure is a double-start closure.
 20. The improvement of claim 18 wherein the multi-start closure includes at least two helically wound forms, each form being one of a flange form, a v-thread, a square thread, a reverse angle thread and a buttress thread, the form mating with the first helically wound guide and advancement form.
 21. In a polyaxial bone anchor having a shank and a receiver, the shank being pivotable with respect to the receiver prior to locking of a position of the shank with respect to the receiver, the improvement wherein: a) the receiver has spaced arms having inwardly facing surfaces, each surface having a helically wound guide and advancement form located thereon, each guide and advancement form being sized and shaped to mate with a helically wound multi-start closure member having at least two starts.
 22. The improvement of claim 21 further comprising an attachable and detachable guide tool cooperating with the receiver, the guide tool having at least two arms, each arm having helically wound guide and advancement structure thereon in synchronized relationship with the receiver helically wound guide and advancement forms to provide transfer of the multi-start closure member between the guide tool and the bone anchor upon rotation of the closure. 